Understanding Windows Server Client Access Licenses (CALs)

***Disclaimer: this article is from 2018 and information are based on Windows Server 2016 edition. We suggest you to click on Help for Windows Server 2019 Client Access Licenses (CALs) for more update information about the same topic.***


Whether you are a customer or a reseller, it is important to understand the ins and outs of Windows Server Client Access Licenses (CALs) to ensure license compliance is met.

Today, we will explain CALs: what they are, the different types, and why they are important!

Windows Server 2016 Core-Based Licensing
First, let’s start with some basic Windows Server licensing information, we’ll call it 'Windows Server licensing 101'. Starting with Windows Server 2016 Standard edition and Datacenter edition, Microsoft introduced a new licensing model. This new model is based on the cores in the server, (where as previous Windows Server licensing models were based on processors). Although the licensing model has changed, one thing has stayed consistent… the need for CALs!
It is important to note that CALs are only required for Windows Server 2016 Standard and Datacenter editions. For Windows Server 2016 Essentials edition, CALs are not required.

Want to learn more about Core-Based Licensing? We’ve got the perfect video and blog for you! Check it out: Windows Server 2016 Core Based Licensing Explained


Microsoft Windows Server Operating System (OS) Licenses
When a customer purchases a Windows Server OS license (Windows Server 2016 Datacenter edition for example), they receive a license that allows them to install the operating system onto the server. However, the Windows Server OS license does not give them the legal right for users or devices to connect to the server… that is where CALs come in!

Microsoft Windows Server Client Access Licenses (CALs)
A Windows Server CAL is a license that allows customers to access Windows Server. CALs are used in conjunction with Microsoft Windows Server OS licenses to allow Users and/or Devices to access and utilize the services of that server OS.

If your customers are wanting to run Windows Server 2016 on their new HPE Gen10 server, they would acquire a Windows Server 2016 OS license in order to run the Windows Server software on the physical server AND they would need to acquire CALs for the Users or Devices who will access the server.

This two-component license models provides a low entry price and a way to pay for capacity used: the more devices or users accessing the server software, the greater the license fees or price. This model therefore offers license affordability to organizations of all sizes.


What are the different types of CALs?
HPE offers several different types of Windows Server CALs.

  • User CALs allow a single user access to Windows Server from an unlimited number of devices
  • Device CALs allow an unlimited number of users to access Windows Server from a single device

Does the organization have roaming employees who need to access the corporate network from several devices? In this case, User CALs make the most economical and administrative sense.

Does the organization have multiple users for one device, such as shift workers using a kiosk-style workstation? In this case, Device CALs make the most economical and administrative sense.

There is a third type of CAL that we must talk about, Remote Desktop Service (RDS) CALs. RDS CALS are required for users or devices that want to utilize Remote Desktop Service functionality on Windows Server. Regular User or Device CALs are required in addition to the RDS User or RDS Device CALs.
CAL types.jpg

More Fun Facts about CALs!
Windows Server CALs can be purchased from Hewlett Packard Enterprise, or an authorized partner, at any time and do not require a new HPE server purchase. HPE currently offers User CALs and Device CALs in packs of 1, 5, 10, and 50 CALs. RDS User and RDS Device CALs are available in packs of 5 CALs.

Windows Server CALs must be the same version as—or higher than—the server software they are accessing. In other words, users or devices accessing a server running Windows Server 2016 must have Windows Server 2016 CALs. Additionally, Windows Server 2016 CALs may be used to access Windows Server 2012 (but Windows Server 2012 CALs cannot be used to access Windows Server 2016).

It is imperative that businesses stay up to date with their CAL compliance requirements so they don’t fall behind or find themselves in error!

Adding new users? More User CALs may be required!

Adding new devices? More Device CALs may be required!

If you are a reseller, now is a great time to check in with your clients to ensure their CAL needs are filled! If you're a customer, now is a great time to check your server environments to ensure you're in compliance!

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About the Author


Willa manages the HPE | Microsoft Coffee Coaching program. Follow along to learn more about the latest HPE OEM Microsoft product releases and how the HPE Microsoft partnership can benefit partners and customers.